J S U N I L T U... CLASS 9 WORK AND ENERGY

J S U N I L
CLASS 9TH
T U T O R I A L
WORK AND ENERGY
Numerical problem
1. A rickshaw puller pulls the rickshaw by applying a force of 100 N. If the rickaw moves with
constant velocity of 36 kmh-1. Find the power of rickshaw puller. (1000w)
2. A athlete weighing 60kg runs up a staircase having 10 steps each of 1m in 30 sec. Calculate
power (g=8.8ms-1 200W)
3. The heart does 1.5 J of work in each heartbeat. How many times per minute does it beat if its
power is 2watt? (80 times) hint: total work =p x t =120J , number times heartbeat in 1 min.
=total work done / work done in each beat=120/1.5=80 times
4. Calculate the time taken 60 w bulb to consume 3000 J of energy . (50sec. )
5. A horse exert a force of 200N to pull the cart. If the horse cart system moves with velocity
36kmh-1 on the level road., then find the power of horse in term of horse power (1hp=746W)
Ans. 2.68h.p
6. An electric kettle of 500W is used to heat water everyday for 2 hours . Calculate the number of
unit of electrical energy consumed y it in 10 days. (ANS. 10 UNIT)
7. Calculate the cost of using a 2kwh immersion rod for heating water in a house for one hour
each day for 60 days if the rate is Rs. 1.50 per unit kWh.
(Rs. 180)
8. How many unit of energy will be consume by a 100 W refrigerator in 30 days , if it works for
16 hrs. Every day.
{48kWh(unit)}
9 . A 1000w oven is used everyday for 90 min. Calculate the unit of electrical energy oven
consume in 30days.
10.
(45 unit.)
The power of a heart which beats 72 times in a minute is 1.2kW. Calculate the work
done by heart for each beat.
jsuniltutorial.weebly.com
( 1kJ)
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